U.S. Pat. No. 3,541,606, issued to S. A. Heenan and R. I. Nagel, discloses a reflector in which the cube corners of the reflector elements thereof are arranged in two or more groups, the elements of one group having aligned cube-corner and element axes inclined at one angle and the elements of the other group having aligned cube-corner and element axes inclined at another angle. Because of the dual-angle configuration, the reflector is visible over a greater zone than would a reflector having all elements similarly directed.
In a cube-corner reflector, the angle between the cube axis and each face of each cube-corner reflector element is nominally 35.degree.16', and the angle between the cube axis and each edge of each reflector element is nominally 54.degree.44'. In a nonangled reflector, in which the cube axes of all the reflector elements are parallel (and perpendicular to the front face of the reflector if it is flat), the angle between all of the cube-corner faces and the front face of the reflector is nominally 54.degree.44', and the angle between the cube-corner edges and the front face is nominally 35.degree.16'. In the angled reflector disclosed in the above-mentioned patent, the cube axes of all the reflector elements are not all parallel, but, rather are angled in different directions. Thus one cube-corner face of some reflector elements is "more nearly parallel" to the front face of the reflector; and one cube-corner edge of the rest of the elements is "more nearly parallel" to such front face. For example, if the angle of inclination were 10.degree. the angle between one cube-corner face of one-half of the reflector elements and the front face would decrease to 44.degree.44', and such angle in respect to the rest of the elements would increase to 64.degree.44'. In the latter elements, a cube-corner edge of each is "more nearly parallel" to the front face of the reflector.
It has been found desirable in certain situations, that one face of all of the cube-corner reflector elements be "more nearly parallel" to the front face of an angled reflector. While there has been a previous attempt at providing a reflector in which each reflector element has one face "more nearly parallel" to the front face of the reflector, such attempt has not been entirely satisfactory. In that reflector rows of cube-corner elements are diamond-shaped in outline. The elements in every other row are angled in one direction, and the reflector elements in the rest of the rows are angled in the other direction. Although each reflector element has a face which is more nearly parallel to the front face of the reflector, it has "shadowing" or "slippage" losses. Also, apparatus used in making such a reflector is cumbersome.